Santa Domitilla

English name:

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Santa Domitilla is a palaeo-Christian complex located at Via delle Sette Chiese 282, just west of the ancient Via Ardeatina and in the Ardeatino quarter. Pictures on Wikimedia Commons are here.

It comprises a 4th century basilica, partly underground and substantially rebuilt in 1870. This is the focus of a very extensive set of catacombs ("Catacombe di Santa Domitilla") -for the introductory article on these in general, see Catacombs of Rome.

Contents

The modern dedication of the basilica is to St Flavia Domitilla, and the catacombs are now also named after her.

However the church is also known as the Basilica dei Santi Nereo ed Achilleo after SS Nereus and Achilleus, and as the Basilica di Santa Petronilla after St Petronilla. These three martyrs were venerated in the catacombs from ancient times, and the basilica was built over the shrine of the first two.

It may be noted that "Achilleus" would have been called "Achilles" when alive, but that the early Christians renamed him "Achilleus" to avoid invoking the memory of the famous Greek hero.

Confusingly, the church is traditionally referred to as a "basilica" but it does not have the dignity of a minor basilica.

"22 June. At Rome, the commemoration of St Flavius Clemens, martyr, who was executed by Domitian the emperor with whom he had been consul, nominally for denying the gods but in reality because of his faith in Christ. AD95."

"7 May. At Rome, the commemoration of St Domitilla, martyr, the daughter of the sister of Flavius Clemens the consul, who during the persecution of Domitian was accused of denying the gods by giving witness to Christ and, with others, was deported to the island of Ponza and endured an extended martyrdom there."

These entries are based on four historical sources:

Suetonious in his De Vita Caesarum(Domitian XV:1) wrote that Domitian executed Flavius Clemens suddenly and on a very slight suspicion, "his cousin of very contemptible inertia" (which seems to indicate that he couldn't be bothered with his public duties as a consul).

Dio Cassius in his Roman History as it survives (Epitome of Book LXVII) wrote "Domitian killed, along with several others, Flavius Clemens the consul, although he was a cousin and had Flavia Domitilla as wife who was also related to Domitian. They were both accused of atheism along with others, having adopted Jewish customs, and were condemned. Some were executed, others had their property confiscated and Domitilla was exiled to Pantelleria." (The Greek literally reads "running aground like a ship into the things of the Jews".)

Eusebius in his Ecclesiastical Historywrote that Flavia Domitilla, niece of Flavius Clemens, was deported to Ponza with several others for having confessed to Christ.

St Jerome in his Epitaph on St Pauladescribed how St Paula visited Ponza and "the little cells in which Domitilla led a long martyrdom". St Jerome was keen on presenting the ascetic life as a form of martyrdom in itself, so this is not evidence that she was actually killed.

It is impossible to obtain a scholarly conclusion on two disputed points:

1) Were SS Flavius and Domitilla Christians, or Jewish proselytes? At the end of the 1st century Christianity still counted as a deviant messianic Jewish sect, although the Roman authorities understood the distinction sufficiently to be able to mount the persecution by Nero. There is a parallel Jewish tradition that "Jewish customs" meant just that.

2) Were there two Domitillas? Either Flavius had a wife and niece of the same name, or he married his niece and one of the sources was mistaken as to which island she was exiled to. The Roman martyrology has preferred the former opinion, and identified the niece as the saint.

Whatever, a cult of St Domitilla obviously existed on Ponza by the late 4th century. On the other hand, none existed in Rome in the Middle Ages -she only began to be liturgically commemorated in 1595. Her profile in the city rested on the fictitious legend connecting her to the other saints of the catacombs (see below).

So, why was her name attached to the catacombs? Epigraphs discovered here have made it clear that this was because she owned at least part of the property under which the catacombs began. The guidebook gives a sample of a (now lost) epigraph delimiting a piece of land with burial rights granted by her:

The first documented reference to her name being attached to the catacombs seems to be in the Einsiedeln Itinerary, which is a pilgrim guide of the early (?) 9th century. The entry reads: Cimiterium Domitillae, Nerei et Achillae at Sanctam Petronillam, via Ardeatina.

The 4th century basilica was deliberately built with the shrine of these two martyrs as its focus and it is clear, from the catacomb layout around it, that the shrine was by then regarded as the central object of devotion of the complex.

Pope St Damasus (366-84), who probably built the basilica (it might be later in the century) composed a metrical inscription for the shrine. Two fragments were found in excavation, but fortunately the text was transcribed in the early Middle Ages. It reads:

("Nereus and Achilleus, martyrs, had put their names down as soldiers and fulfilled a cruel function, together giving regard to the orders of the tyrant and ready to serve through the impulse of fear. A wonderful truth in the matter: suddenly they put aside their rage and, changed, they fled, left behind the impious headquarters of the duke and threw away the shields, kit and cruel lances. Confessing, they rejoiced to bear the triumph of Christ. Believe, by means of Damasus, what the glory of Christ is capable of.")

The Roman martyrology locates this event in the 3rd century.

It is uncertain as to when the relics of the martyrs were removed from their shrine here, as the event was not recorded. The early 9th century is a good guess, as Pope Leo III rebuilt the eponymous church of Santi Nereo e Achilleo in 814. The saints remained there until 1213, when they were moved to Sant'Adriano. They were brought back by Cardinal Baronius at the end of the 16th century, and remain under the high altar of that church near the Baths of Caracalla.

The virgin martyr Petronilla, of uncertain date, was enshrined somewhere in the catacombs behind the apse of the basilica. Archaeologists have been unable to pinpoint the exact location, and this is because her relics were in a moveable sarcophagus with apparently no fixed shrine fittings. However, a 4th century fresco featuring her is extant and must have been near the shrine.

The sarcophagus was a luxury item, of coloured marble carved with four dolphins and with the epitaph Aureliae Petronillae filiae dulcissimae.

This sarcophagus and her relics were taken to St Peter's in 757, and enshrined in the adjacent church of St Petronilla. This church became the national one of France. In the Middle Ages there was a popular legend that she was the daughter of St Peter, a delusion that probably arose from her name. The apocryphal Acts of Peter features a paralysed daughter of the apostle, temporarily healed by him, but the invalid is not named. (From the 17th century, liturgical texts described St Petronilla as a spiritual daughter of the apostle, owing to uneasiness over the implications of one of the apostles having been married.)

The church of Santa Petronilla was demolished by Bramante at the start of the 16th century when the rebuilding of St Peter's was begun, and incredibly her sarcophagus was smashed up to provide marble inlay. However she has an altar in the present basilica, and her relics are enshrined there.

In the 6th century, a work of romantic fiction was written which involved SS Peter, Petronilla, Domitilla, Nereus and Achilleus in its plot-line. This Passio SS Nerei et Achillei is a rambling tale, featuring the two martyrs as eunuchs in the service of St Domitilla. The anonymous author was obviously unfamiliar with the already extant tradition that SS Nereus and Achilleus had been soldiers, but was familiar with the association of their catacombs with St Domitilla. This is a puzzle.

A clue to provenance might lie in the assertion that the saints were martyred at Terracina.

The story had its influence on later liturgical texts celebrating these saints, including those of the Eastern churches as it was translated into Greek soon after it was written. However, the Second Vatican Council decreed that obviously fictitious legends concerning saints were to be deleted from such texts in the Roman rite and this was done in 1970.

The pretence that the Passio was an historical document caused it to be treated with contempt by historians until recently ("sad rubbish" was one comment found in print), but nowadays it is appreciated that it is a rare survival of late Roman Empire fiction and worth attention as such.

The remote origins of the catacombs have been obscured by romantic imaginings, and also by the very unsatisfactory state of the archaeological investigations of the surface area. Unfortunately 19th century investigators took the legend of St Domitilla as indicating that the gens Flaviaestablished a Christian hypogeum on the property in the late 1st century, and that this was the beginning of the catacombs. Giovanni Battista De Rossi published this assertion in a write-up of his investigations in 1865, and Joseph Wilpert concurred that the frescoes which the "Flavian Hypogeum" contained were 1st century Christian art. Unfortunately, neither assertion could be backed up by evidence from the hypogeum itself. A fragmentary epigraph reading ...rum ....iorum was discovered and read as sepulchrum Flaviorum ("tomb of the Flavians") -a gross example of wishful thinking in palaeography.

This criticism notwithstanding, De Rossi and Wilpert were seriously impressive scholars for their time.

Letizia Pani Ermini published her conclusive revisionist analysis in 1969 which demonstrated that the hypogeum began as a pagan tomb in the mid or later 2nd century, and was Christianised in the mid 3rd century.

Excavations on the surface in 1960, interrupted by worries about ground stability, revealed evidence of three pagan funerary complexes on the surface which had been enclosed by a wall in opus reticulatum. These included niches for cinerary urns as well as for interments, and an actual urn was found in a second such enclosure. The probable date of these enclosures is in the 1st century AD, and marks the beginning of funerary activities on site (a Republican dating for the beginning of burials here is unsupported by evidence). The epigraphs mentioning Flavia Domitilla derive from this early activity. No piety on her part needs to be presumed -developing an extra-mural property for funerary purposes could be very profitable, as demand in ancient Rome was high.

The underground complex began as a number of independent, privately owned pagan hypogea. The most notable of these has already been mentioned, the so-called "Flavian Hypogeum" which was excavated by an unknown family or wealthy confraternity at the end of the 2nd century by the latest. The "Hypogeum of the Good Shepherd" is thought to be early third century in origin, and is the earliest part of the complex to demonstrate the classic catacomb layout of separate rooms (cubicula) connected by passageways. The "Hypogeum of Ampliatus" dates from the second half of the third century, but was also probably pagan in origin (by this time, Christian activity is discernible in the complex).

The arrival of Christians in the complex is only discernible from the evidence of overtly Christian elements in frescoes and epigraphs. These are only certain from the mid 3rd century, which is the date assigned by Pani Ermini to a fresco with Old Testament scenes in the Flavian Hypogeum. It is thought that another early focus of Christian activity was the so-called "Flavian-Aurelian Hypogeum" to the south of the basilica, which actually comprised two poor-quality hypogea perhaps dug at the end of the 2nd century and connected up as a small catacomb later in the mid 3rd century.

The martyred soldiers SS Nereus and Achilleus are thought to have been buried in a cubiculum in this catacomb in the latter half of the 3rd century, and St Petronilla was interred close by at an unknown date.

It is thought that the complex was Christianised as a whole by the end of the 3rd century. The responsibility for funerary activities seemed, according to epigraphic evidence, to have been with the clergy and people of the titulus fasciolae located near the Baths of Caracalla. (This is now the church of Santi Nereo e Achilleo, and contains the relics of the martyrs.)

The so-called Peace of the Church under the emperor Constantine saw a massive expansion of the complex. It is a long-established error to assume that the extant catacombs of Rome were dug during the periods of persecution up to the 4th century -most of them were excavated in this century. The result at Santa Domitilla was a set of passages thought to amount to about 12 kilometres (other sources raise this to 17).

The geological nature of the site was not really suitable. As a result, there are only two main levels to the catacombs. Most of the passages are to the south of the basilica, and are fairly regularly laid out. Below these, the tufo rock becomes too soft to be safe and also the water table is too close. However, around the basilica itself is a chaotic and close-packed area of passages including limited third and fourth levels further down. This is taken as evidence that there was demand for grave-spaces near the shrines of the martyrs.

As in other catacombs, the burial facilities involved loculior horizontal slits in the passage walls for the cheapest interments, arcosoliawhich were larger and fancier recesses and finally cubicula or little rooms for rich folk, families or confraternities. There are about eighty frescoed arcosolia and cubicula, and the total number of burials is estimated at 154 000.

The cubiculum which originally housed the martyrs' relics is thought to be represented by an extant section of vault and a short access passage behind the basilica's apse. The passage has geometric fresco decoration and chi-rho symbols, dating from after 313. This cubiculum was replaced by a small trapezoidal shrine chamber in brick, about six by seven metres, into which the relics seem to have been transferred from their original graves -perhaps for ease of veneration (this chamber is now the far right hand corner of the basilica).

Most of the original cubiculum, together with several other cubicula and passages in the second level, was destroyed when the basilica was built. This involved an approximately rectangular trapezoidal excavation being made down to the level of the martyrium, in order to accommodate the new church. The dating of the work is a problem. It was either done by Pope St Damasus (366-84), in which case the trapezoidal shrine chamber was provided about the year 320, or Pope Siricius (384-99). If the latter, then the trapezoidal room was by Damasus. The argument for Siricius rests mainly on the style of the basilica's fabric. Both dates find favour in modern publications.

An alternative date for the basilica of around the year 600 was proposed by Krautheimer 1967 and supported by Tolotti 1985, but has not been generally accepted. The argument rests on points of architectural style, as the layout is very similar to the 7th century basilica at Sant'Agnese fuori le Mura.

The basilica and the catacombs remained as a working funerary and pilgrimage complex for the next four hundred years, and the basilica itself was a popular place of burial.

The Liber Pontificalis records that Pope John I (523-6) restored the complex. In the basilica, this seems to have involved the building of a schola cantorum (choir enclosure in front of the apse), and major repairs. The apse had cracked and was partly rebuilt, and the last column of the right hand arcade was buttressed. This is fairly clearly as a result of earthquake damage.

Pope St Gregory I (590-604) preached his twenty-eighth homily in the basilica (the text of it is here), so the church was fully functioning then.

The last historical record of the complex is for the reign of Pope Gregory III (731-41), who instituted an annual stational pilgrimage to the catacombs (in cymiterio Beatae Petronillae) and donated precious items to the basilica.

The date of the abandonment of the basilica and catacombs is unrecorded, but the event was in the context of the more general abandonment of the city's suburban surroundings in response to bands of Lombard, Muslim and home-grown marauders in the 9th century. All the catacombs except those at San Sebastiano fuori le Mura, San Pancrazio, Sant'Agnese fuori le Mura and San Valentino were stripped and left derelict. (In the event, only the first-named kept its catacombs open throughout the Middle Ages).

Pope Leo III rebuilt the church of Santi Nereo e Achilleo near the Baths of Caracalla in 814, which had been the titulus Fasciolae responsible for the catacombs from the 3rd century. This is the plausible date for the transfer of the relics of SS Nereus and Achilleus, and the stripping and abandonment of their basilica. Even the floor was taken up and removed.

There is evidence that access to the catacombs was still maintained via a pathway through the narthex of the basilica and down the right hand aisle to an entrance at the right hand side of the apse (still used for visitors).

The final destruction of the basilica is thought to have been in an earthquake in 897 which topped the columns of the arcades, and left them lying parallel to one another for De Rossi to find when he excavated in 1873.

Amazingly, the site was then completely forgotten about for 700 years despite being on a pilgrimage route between San Sebastiano fuori le Mura and San Paolo fuori le Mura. This is the present Via delle Sette Chiese, a reference to the Seven Church Walk which remains popular to the present day (although the traffic is now the danger, not the bandits).

When De Rossi dug out the ruined basilica, he was not interested in how the fill got there -so we don't know at what stage the local country folk thought it worthwhile to fill in the big hole in the ground, which would have been dangerous to their livestock.

The location was so thoroughly forgotten that Santi Nereo e Achilleo was thought to have been the original basilica. So, when Antonio Bosio rediscovered the complex in 1593, it was thought to be part of the Catacombe di San Callisto. He was eighteen at the time, and this was his first catacomb exploration. Bosio got in via the Flavian Hypogeum, and wrote about how he got lost and spent most of a day underground (he was lucky not to have died). An "I was here" graffito by him is extant.

Subsequent visitors were often destructive. Epigraphs were pillaged, loculi were smashed open to extract "relics" (the delusion that the catacombs were stuffed with martyrs was in full force), sarcophagi were stolen and even frescoes were lifted off the walls and removed. For example, the official antiquarian Marcantonio Boldetti discovered the "Cubiculum of Diogenes the Fossor", sketched the frescoes and then destroyed them when trying to remove them. Fortunately, he published the sketches in 1720.

From 1816 to 1823, Duchess Marianna di Chablais employed Luigi Biondi in archaeological investigations on the Tor Marancia estate. Most of the discoveries were ancient Roman (including the Villa of the Numisi), but it is thought that the famous Sarcophagus of the Passion (now in the Pio Cristiano Museum in the Vatican) was extracted from somewhere in the catacombs by Biondi. There is an article on this artefact here.

The modern period of the history of the catacombs begins with the work of Giovanni Battista De Rossi (the archaeologist). He began in 1854 with the discovery of another entrance, called the "Tor Marancia Grand Staircase" or the "1854 Staircase" which was an ancient access to the area of the "Cubiculum of the Good Shepherd". The Casale di Tor Marancia was the local farmstead in this area, which then was completely rural.

In the same year, De Rossi managed to penetrate into the basilica area and began investigations there. Unfortunately, his work precipitated a landslide and the local landowner expelled him. Even more unfortunately, carved stonework that had been uncovered was then looted.

It was only at this point that the true identity of the catacombs as those of St Domitilla was finally established.

De Rossi was only able to resume operations in 1873, when Archbishop Xavier de Mérode bought the estate and paid for the excavations. The first campaign involved the clearing out of the basilica. Exploration of the catacomb passages continued for the rest of the 19th century, with the so-called "region of the six saints" being mapped in 1899.

Orazio Marucchi continued archaeological investigations in the early 20th century, publishing his results in 1909 to 1914. Unfortunately, he was uncritical as regards the mistaken early dating of the Christian occupation of the catacombs. His Guida del Cimitero di Domitilla was published in 1923, and remained the standard guidebook for many years.

In 1910 he traced three grave-slots in the floor of the basilica's apse, flanked by three settings for sarcophagi, and identified these as the original burial places of the martyrs -they might have been privileged burials after the basilica was built, however.

The rebuilding of the basilica was undertaken in 1912. The work was done by the simple expedient of raising the surviving walls to above ground level and putting a roof on top. The result was then re-consecrated as a working church, with a small attached convent.

Further investigations of the surface remains were undertaken after 1926 when a 1st century funerary enclosure wall was accidentally discovered, but the main excavations here were in 1960. These were abandoned uncompleted after a landslide, and no further work has been done on the surface since.

The immediate surroundings of the basilica are still green fields, but the suburb of Tor Marancia is close by and the southernmost galleries of the catacombs are now under apartment blocks. This causes concern, since the suburb was badly planned and built. There have been collapses in the catacombs in recent years. Also, the water table has risen in recent years and the small "fourth level" under the Flavian Hypogeum (the lowest part of the catacombs) is now flooded and inaccessible.

From 2006 to 2009, the entire set of catacombs was laser-scanned to produce a virtual reality model. This was done by a team led by Norbert Zimmerman of the Vienna Academy of Sciences. In early 2016, it was hoped that publication of the model would occur later in the year (see "External links" for an interim report).

On the surface, the catacomb site has two enclosures separated by the road.

To the north, there is a grassy paddock with a wall around it bearing the huge legend Catacombe S. Domitilla. This contains the original entrance before the basilica was rebuilt, which is against the far wall and leads down into the Flavian Hypogeum. There is no public access to this enclosure.

To the south is the present catacomb service complex, focused on the basilica. The car park is to the west, and there is an L-shaped convent attached to the basilica to the east. A separate flat-roofed block in pink render is between the basilica and the road, and the architectural main entrance is to the east of this (left hand side, looking from the road). However, this is never open to the public.

The complex includes an attractively laid-out garden behind the basilica.

Externally, the basilica itself is not very impressive because much of it is underground. It is a low trapezoidal structure in a mix of red brick and yellow tufo blocks, with a row of nine round-headed windows at the west end (these are above the apse). Above the middle window of the row is a little round window, below the gable of the pitched and tiled roof.

Reception and tickets are in the two-storey white-rendered wing at the far side round the back.

When built, the basilica had a five-bay nave with aisles, and an apsidal sanctuary. In front was a narthex occupying the entire width of the church. Since the church was partly underground, an indirect access was provided which consisted of a stairway running down parallel to the frontage to the front left hand corner, a short second set of stairs round the corner and a final short stairway through the left hand side wall of the narthex. An identical arrangement provides access for visitors today.

Overall, the basilica had a trapezoidal plan with the aisle side walls diverging, and the apse wall on a diagonal alignment away to the right. This far right hand corner involved an extension of the right hand aisle to create a vestibule for the main entrance into the catacombs (there were, however, at least three other entrances).

The dimensions are 20 metres long, with the central nave varying from 8.5 metres (near end) to 10 metres (far end) wide. The side aisles are 3.5 to 4 metres wide.

The side aisles were separated from the central nave by colonnades of four columns each. These are spolia, looted from ancient buildings, and are mis-matched with differing heights. For this reason it is thought that the columns supported arcade arches rather than trabeations, but the complete lack of any archivolt elements in the excavated material should give pause for thought. The putative arcades sprang from engaged rectangular piers flanking the apse, and from a pair of T-piers flanking the entrance from the narthex.

This main entrance from the narthex had a pair of columns -again, three arcade arches are postulated here. There was a side entrance into the left hand aisle, but a matching entrance into the right hand aisle was blocked at some stage (6th century?) and a screen wall built so as to turn the right hand end of the narthex into a self-contained chapel.

It is thought that the side aisles were fully underground, and that the central nave rose above ground level and had windows in its side walls. Galleries (matronea) have been postulated over the side aisles, on no good evidence.

The apse was occupied by the shrine, involving a baldacchino or ciborium. In the 6th century an enclosed choir or schola cantorum was built in front of it, in the further three bays of the nave.

The original decoration of the basilica is a mystery, amounting to a scholarly worry. The archaeologists excavating at the end of the 19th century were on the lookout for any fragments of painted plaster from the interior walls, and for any loose tesserae from mosaics. A mosaic in the conch of the apse was postulated, and it was expected that the inner wall surfaces had been plastered and frescoed. Absolutely no trace was found either of plaster or of mosaic.

The walls of the stairway down into the basilica display sculptural fragments, including many from broken-up sarcophagi.

The present interior is a cuboidal void, with elements of the ancient structure standing isolated including the eight side arcade columns and the two narthex entrance columns. However, the latter and one of the arcade columns are replacements from elsewhere, because the originals were looted in between their discovery in 1853 and systematic excavation in 1873. De Rossi described the missing narthex columns as "African marble", and noted that three of the arcade columns were of cipollino. One of these was looted as well.

You can also see the foundation walls of the schola cantorum with its oddly off-centre near entrance, but the floors overall are not original. These were scavenged when the basilica was abandoned, so the random paving now there was laid in the restoration.

Note the odd appearance of the far right hand corner, which has a very tall archway containing the catacomb entrance used for visitors. The pier wall to the right of the apse is thought to have originally belonged to the cubiculum in which the martyrs were originally buried, and the side and far walls are thought to belong to a pre-existing shrine chamber built to replace this before the basilica was itself built.

There are two very good carved sarcophagi in the narthex, found in the excavations -again, one of these is a replacement from elsewhere of a looted original which De Rossi had noted in 1853.

There are very many epigraphs on the basilica walls (the number from the catacombs is about 900 in total), the most important of which is the epigraph of Damasus in the middle of the front wall of the narthex. Note that only the two lower corners of this are original -the rest is modern, the text being derived from manuscript sources. Also displayed are more sculptural fragments and bits of sarcophagi.

Flanking the altar are bits of the ciborium or marble canopy of the shrine. These include a marble column bearing the name Achieus above a relief description of the martyr about to be beheaded. Behind are depicted a cross and a wreath. This column is presumed to have had a companion depicting Nereus, and a fragment with a broken relief carving of the lower parts of two people is thought to belong to it.

Also here is a large circular marble plate with a raised lip. This is a lanx, and was used to hold little lamps burning in front of the shrine. It was found in bits by the excavators, and the surmise is that it was dropped and broken while the basilica was being stripped for abandonment.

Finally, fragments of transennae or pierced marble screen-slabs are displayed.

The description below starts from the far right corner of the basilica, which is where guided tours enter the catacombs. It then proceeds clockwise, which is the direction of the standard tour.

The more familar regions of the catacombs are labelled with letters of the alphabet, with notable individual locations having number suffixes. The first passage that you enter from the basilica is B, and runs just north of west.

Many locations with wall-paintings have been preserved in these catacombs but, owing to conservation concerns, some of the most notable are not being shown to ordinary visitors any more. The saddest example of this is the famous Cubiculum of Veneranda, third on the left down corridor B.

So many loculi were dug into the walls of this little chamber that its structural integrity was weakened, and so an arcosolium at the back had its lunette arch infilled. This arcosolium has a tabular surface in front of it (which is now a consecrated altar) and in the year 356 a lady was buried in a grave cut in this. Her marble epitaph is on the left side of the lunette, giving her name as Karisia.

The other half of the lunette was frescoed afterwards, and shows a Roman lady called Veneranda being introduced into Paradise by her patron, the martyr St Petronilla. This 4th century painting has an historical interest, since it records the contemporary veneration of saints among lay people, and in particular it documents that the concept of patron saints is an ancient tradition. The identity of St Petronilla is uncertain, but she was known later as the Succour of the Frankish Nation. During the pontificate of Paul I (757-767) her relics were moved to the Chapel of the Frankish Kings (also known as the church of Santa Petronilla), next to San Pietro in Vaticano. This was demolished with the sanctuary of the old basilica at the start of the 16th century.

The lady is depicted in the oransposition, in a loose orange robe with a blue veil on her head and a bush of red roses to her right. Above is an epigraph reading Veneranda dep[osita] VII idus ianuarias. The year of her burial is not given, but the recording of the date was the purpose of holding an anniversary refrigerium or memorial banquet in her memory. The present altar would have served as the table for her, and for the refrigeria of the others buried here. (It is well to note that the old idea that these tables were intended as altars for saying Mass is simply rubbish.) Behind her to her right is Petronilla, identified by the epigraph Petronella mart[yr] and dressed like an empress in tunic and pallium. The martyr points to a lidded round box (capsa) filled with papyrus scrolls, and above this box is floating an open codex (what we call a book).

Unless you are fortunate, your guide won't take you to see the above but will bear first right once in the catacombs. This is passage C, and the fourth turn on the right puts you in a large cubiculum with a exit in the far side. The guide will probably stop here and give a spiel about burial practices when the catacombs were in business, and also about the four levels of passages to be found here.

This cubiculum counts as a chapel, and contains a free-standing altar added at the end of the 19th century. The walls are full of smashed-open loculi.

You are in the second level of the catacombs. Most of the first level is off to the south of the complex, but there is some above you here and to the east. The second level took over the Flavian Hypogeum which you are about to visit, and the third level extends in a restricted area from here to to under the floor of the basilica.

A very small fourth level is to the west of the Flavian Hypogeum. This seems to have been the result of a single project on behalf of a rich family, and consists of a pillared cross-shaped cubiculum from which four broad passages with cubicula and loculi radiate. There is a well, useful for making the mortar used to seal the tombs after interments.

Unfortunately this fourth level is now flooded out owing to a rising water table, and is inaccessible.

From the exit of C1, you turn right into passage D which has a couple of its cubicula used to store ancient pottery vessels including oil lamps. This passage runs just south of east, and ends in a junction with a wide staircase down to the third and fourth levels. Here passage E runs south-east, and the first turning on the left leads into the Flavian Hypogeum. The actual hypogeum (in contrast to its original entrance arrangements, see below) is also known as passage F or the Gallery of the Sarcophagi.

This wide passage or gallery has niches for four sarcophagi -looted long ago. It is now dated to the latter 2nd century AD, and its original fresco cycle to the first quarter of the 2nd century. This was pagan, not Christian. Tragically, it has suffered huge damage from looters and vandals -and also from loculi being hacked into the walls when the gallery was annexed to the larger system of catacombs. Graves were also dug in the floor.

The focus of the original pagan fresco decoration was a large grapevine with birds and amorini (miscalled cupids) picking grapes. The style is in the arte severianafeaturing blank wall spaces, little figures and thin red and green lines dividing the surfaces up. The first Christian additions here date from about the year 260 -notable is a Daniel in the Lions' Den which is being destroyed by rising damp.

The really fascinating part of the hypogeum is its entrance arrangements. The original late 2nd century portal was in a steep slope created possibly by ancient quarrying, and had a single doorway in a very finely laid yellow brick revetment wall. Above the entrance was a large rectangular epigraph tablet, now lost. In the mid 3rd century a shallow vestibule was built in front of this, in the same style of brickwork but of slightly lower quality. The two narrow side walls each had a brick bench provided. This structure is thought to be contemporary with the earliest Christian activity in the catacombs.

Bear in mind that when the catacombs were working, this entrance portal faced the outside world.

To the left of the entrance (looking out) a banqueting hall was built at the end of the 3rd century -the fabric is in opus mixtum or a combination of brick and stone. This was for the celebration of the refrigerium, a meal eaten in honour of the deceased on the anniversary of his or her death. This was an ancient pagan custom, the idea being that the spirit of the dead person would actually get nourishment from joining in. Early Christians carried on the custom into the 5th century, although the thoughtful ones among them are on record as raising objections on theological grounds.

Here, the vault and the front wall have vanished but the revetting wall shows two blind arches and has a low stone bench which would have run round the interior. This is interrupted by the portals of two cubicula, one excavated in the 4th century after the hall had been built and the other pre-existing. The latter is the Cubiculum of Eros and Psyche.

It may be noted here that this hall was never a church, despite a long-held belief asserting this.

This cubiculum was dug and frescoed in the second half of the 3rd century, and was originally pagan. It was respected when the refrigerium hall was built, however. The frescoes depict flowers and birds, with three scenes showing Cupid and Psycheas infants picking flowers. Psyche is shown with butterfly wings, a sexual innuendo.

To the right of the entrance (looking out again) is a water supply for the complex. This comprises a cylindrical well carved from a column drum, in a deep niche with a slightly curved ceiling. The well-shaft is eleven metres deep. The right side of the niche abuts a water tank, and in the front of this is a spigot over a sink on the floor. There should be an amphora in the sink, illustrating how the system worked. Water would be hoisted from the well and poured into the tank, and then decanted from that into amphorae.

Many amphorae were found hereabouts, and are now in the more recent cubiculum off the refrigerium hall. The water was used in banquets, cleaning and in making mortar for sealing tombs.

The painted decoration of the well niche is almost intact, being in yellow over red with the former area having red lines and small vegetal motifs.

Needless to say, early investigators labelled this set-up as a baptistery. It was not.

You return back up the Gallery of the Sarcophagi to passage E, and turn left to continue south-eastwards. The first right is passage E2, where the guide should point out the Cristor epitaph. The interesting thing about this is that it shows a refrigerium banquet with the deceased (a little girl, aged four) taking part. Cristor was the father -the child is un-named (Cristor filiae suae, Criste in pace anis IIII).

At the end of passage E2, turn left into the long passage G. This ends in cubiculum G2, which has to the right of the entrance a very interesting frescoed arcosolium of the mid 4th century. The lunette at the back shows Our Lady (?) flanked by SS Peter and Paul, while the intrados (the under-surface of the arch) is completely occupied by a fresco of Christ with the twelve apostles.

The far side of G2 has an exit, leading immediately into corridor H. Turn left, and the second left is the entrance to the Cubiculum of the fossor Diogenes. A fossor was one of the workmen who actually excavated the catacomb galleries and tombs, and by the end of the 3rd century was a Church employee.

Many of the frescoes here were destroyed in an attempt to remove them at the beginning of the 18th century. However, the arcosolium has Christ between SS Peter and Paul on the intrados, and a depiction of the fossor on the lunette. This shows him with a pickaxe and lantern.

The standard tour finishes here, by going back down passage G and taking a left into passage G1 which runs south-east to the left hand corner of the narthex of the basilica where you emerge.

If, instead of returning down passage G to the basilica, you were to continue down passage H westwards, you would find it curving south and ending in a long staircase. At the top of this, to the left, is an arcosolium completely covered by mosaic decoration -a very rare feature. This was actually discovered and recorded in 1742, but the location was forgotten until 1960 when it was re-discovered during the clean-up needed after a cave-in.

The lunette shows Christ with two saints (unidentified -Peter and Paul?), and an epigraph reading Qui filius diceris et pater inveniris ("You are called the son, and are found as the Father") which is, on the face of it, not correct Trinitarian doctrine.

The intrados shows The Three Youths in the Fiery Furnace and The Raising of Lazarus; a former scene of Moses Striking the Rock has fallen off.

Access to areas of the catacombs to the south and south-east of the basilica is via an iron staircase just by the entrance in the left hand side of the narthex. The very early Cubiculum of the Good Shepherd (L5) is about 75 metres due south of this point, accessed via passages K and L.

This is one of the original core areas of the catacombs, and began as a hypogeum possibly containing three burials in sarcophagi which was dug in the first decade of the 3rd century (the dating relies on the style of the vault fresco). At the end of the same century the floor was lowered to make room for two arcosolia. These are also frescoed.

The vault fresco might be the earliest Christian one in the catacombs. It has a white background, on which were drawn red and green lines forming geometric shapes. A central roundel contains a figure of The Good Shepherd, partly destroyed by a damp patch, and this is surrounded by a large circle divided into eight unequal sectors containing vegetal motifs (garlands, teasel plants) and four pigeons. The vault corners have quarter-circles containing birds.

At the end of passage L, beyond the Cubiculum of the Good Shepherd, is a wide and long staircase which was one of the main entrances of the catacombs. It was dug out at the start of the 3rd century to access two levels, which were lit by a large skylight shaft in between the staircase and the above-mentioned cubiculum which is in the second level. The rediscovery of the staircase was in 1854, and is counted as the beginning of the scientific study of the catacombs here.

Near the bottom of the staircase in the second level is a cubiculum from which frescoes have been looted but which still has one of David with his sling, about to challenge Goliath (not shown).

The staircase is a very convenient access to the first level here, which contains further interesting frescoed cubicula. Passage M runs just west of south for about 60 metres to the Cubliculum of Ampliatus, another very old core feature of the catacombs with its own (now lost) entrance arrangements. It was discovered in 1881.

The deteriorated frescoes are difficult to date, but it is thought that the original hypogeum was dug in the early or mid 3rd century for a family of freedmen belonging to one Ampliatus. We know this, because an epigraph survives which tells us. There is no evidence from the surviving fresco work that he was a Christian.

The hypogeum consists of two conjoined cubicula separated by a support arch constructed after a vault collapse in the 4th century (around the same time as the hypogeum was connected to the catacomb system). One cubiculum still has the original decoration, consisting of fake architectural elements in the form of panels and columns forming an entablature. The second cubiculum had at least two re-paintings, including five country scenes of animals grazing. The vaults are painted with large bunches of grapes, done after the support arch was erected.

A little further on down passage M is the Arcosolium of the Twelve Apostles, labelled M3. This has a very good mid 4th century fresco on its lunette showing Christ in the midst of the apostles, all shown as young men. Christ has no beard -that came later in artistic tradition.

It seems strange now, but the lower half of the fresco was destroyed by a loculus being cut into it. This sort of destruction of pre-existing artworks in order to make room for more burials was actually common in the working catacombs.

One of the two rooms of the Cubiculum of Ampliatus has an exit leading to passage N. At the end of the latter is a cross-passage P, and on the first right after turning right is the Cubiculum of Orpheus. This is one of the most sumptuous cubicula in the catacombs.

This cubiculum has three arcosolia, a slightly curved vault and engaged Doric columns in the corners. All wall and vault surfaces are frescoed. Over the arcosolium to the right is a depiction of Elijah Ascending into Heaven (the prophet Elisha) is shown to the left. The far arcosolium has Orpheus Taming the Beasts on its lunette, and on the wall over the niche is Moses Striking the Rock and Micah Indicating Bethlehem (Mic 5:2). In between these was a depiction of the Madonna and Child, now destroyed.

Despite being the subject of a pagan myth, Orpheus seems here to be a symbol of Christ.

Corridor P in the other direction takes a curving course northwards and ends up back at the 1857 staircase. On the way it passes the Cubiculum of the Six Saints (P3), which has an arcosolium fresco showing Christ handing out laurel wreaths to six people (three men and three women). This is a symbolic depiction of martyrdom, although it does not indicate that those buried in the cubiculum were actually martyrs.

This area of the catacombs is called the "Region of the Six Saints", and is a large zone on two levels created in the mid 4th century.

The same set of stairs from the basilica narthex as lead eventually to the Cubiculum of the Good Shepherd, also leads to a first-level area labelled Q, R and S running in a south-westerly direction. It is rich in frescoes. Staircase Q leads off passage L.

Unfortunately, the geology in this area is proving unstable and there have been recent roof-falls.

The most famous of the frescoed cubicula here is the best example in these catacombs of a cubiculum being sponsored by a trades guild in the mid 4th century. A corporation of bread-bakers commissioned superb frescoes in here, including a finely executed Christ the Teacher Enthroned Among The Apostles and Christ the Good Shepherd. Hard to identify now are small dado scenes showing workers unloading sacks of wheat from trans-shipment boats on the Tiber.

Near this cubiculum was a fresco of a barley-miller, but this has been lost in a roof fall. Also nearby is a graffitio reading "Bosio", left by Antonio Bosio when he explored in 1593.

Finally, just to the south of the basilica and with its own access stair from the left hand aisle, is a restricted area formed when two very old hypogea were united with the rest of the catacombs in the 4th century. They were dug at the end of the 2nd century, and united into a single small complex in the mid 3rd. A recently discovered entrance staircase for "Hypogeum B" is to the east, which was the access for this complex when it was remodelled. Remains survive of the independent staircase of "Hypogeum A", abandoned then.

It is surmised that these two little hypogea were the first Christian tombs in this locality, but lack of fresco or epigraphic evidence makes this hard to prove. Noteworthy is that the galleries were dug deeper to accommodate more loculi, making the top ones unreachable.

While not related to the catacombs, this Ardeatine Caves (Fosse Ardeatina) memorial located nearby should be mentioned, as it's practical to combine the two sites in one visit.

On 23 March 1944, the Italian resistance group GAP killed 33 German members of the SS Police Regiment Bosen by means of a bomb in Via Raselli. The reprisal chosen was that ten Italians were to be killed for each German soldier, and according to orders directly from Hitler, this was to be carried out within 24 hours.

Pope Pius XII appealed on behalf of the victims, but in such a short time nothing could be done against an order from Berlin. 335 Italians were taken from various prisons and shot at the Ardeatine caves. They were buried at the spot by means of collapsing the caves with high explosives. In March 1998, former SS officers Erich Priebke and Karl Hass were sentenced to life imprisonment in a Roman court for their roles in the massacre. The memorial is a strong reminder that persecution and inhumanity is not only something of the distant past.

The site is a national monument and cemetery, as the bodies were re-interred here. Surviving relatives and descendants often visit on Sundays, but no formally consecrated place of worship is included in the complex. Partly this is because many of those massacred had Communist connections, and a few were Jews.

The basilica and catacombs are open six days a week, 9:00 to 12:00 and 14:00 to 17:00.

Closed Tuesdays. There is also a Christmastide closure, from mid December to mid January.

Note the lunchtime closure. If you find yourself waiting for the afternoon opening, you can have a picnic lunch here -there are tables in the garden.

Entry is by a guided tour -this is not optional. The last tour is apparently fifteen minutes before closure.

As at 2016, the ticket is eight euros (five euros for concessions).

Word has it that the tour is shortened in busy periods, as also happens at Catacombe di San Callisto. This noisome if understandable practice means that serious visits are best made in the winter months. Whatever, you should be shown the Flavian Hypogeum, the Arcosolium of the Little Apostles and the Cubiculum of Diogenes. The total length of the underground tour is advertised as half a kilometre.

Many of the most interesting frescoed areas are now permanently off limits to visitors, owing primarily to conservation concerns.

It used to be the case that one could negotiate with the guides, especially at quiet times, in order to be taken to areas not normally shown to visitors. Be aware that this sort of old-fashioned Italian courtesy is now seriously discouraged by the Vatican authorities in charge of the catacombs -it is not worth asking. Those with serious scholarly interest may (or may not) obtain access to closed areas through the Vatican scheme concerning Visits to Catacombs Closed to the Public. This scheme is discretionary.

These catacombs are unique among those open to the public in Rome, in having a church exclusively used for liturgical celebrations by pilgrims. There does not seem to be a fixed timetable of Masses, as there is no other pastoral responsibility.

If your group wishes to celebrate Mass in the basilica and you have your own priest, you need to contact the Divine Word Missionaries in charge of the complex in good time beforehand.

There are altars in locations within the catacombs themselves, but these do not seem to be used any more.